This is the spot where the Australian states of New South Wales, Queensland and South Australia meet. Nineteenth century surveying methods resulted in boundaries that were not quite accurate. If you use modern surveying methods or just an ordinary GPS device that is accurate within a few metres, you might think the marker is in the wrong spot. The governments of the three states have agreed that the boundaries, as surveyed in the nineteenth century, remain the legal and accurate boundaries. In this picture, east is at the top, north is left.
See map in OpenStreetMap.
At Cameron Corner, there is no direct road between New South Wales and Queensland. The wild dog fence precludes any crossing between the states at this point. However there is a gate from New South Wales into South Australia. Once in South Australia, one can travel a few metres west, then turn north for a few more metres before turning east into Queensland. The only civilisation in the area is the Cameron Corner Store which is a roadhouse just across the border in Queensland. Even though the the "civilised" part of Cameron Corner is in Queensland, it has a New South Wales postcode and South Australian phone number.
South Australia always operates on a different time zone to New South Wales and Queensland so that, in the cooler months of each year (approx April to September), any given time of day happens in two states and then happens again half an hour later just millimetres away in South Australia. From approximately October to March, each of the three states operates in different time zones so that New Year's Eve can be celebrated multiple times at Cameron Corner.
For more, see Wikipedia
Border crossing at Cameron Corner